(1) Field of the Invention
The present invention is a broadband in-line amplifier. This amplifier is part of a towed buoyant cable antenna system that is deployed in seawater. In the present system an antenna element is comprised of a termination tip that is connected to a buoyant cable. The termination tip is grounded to the seawater. The in-line broadband amplifier is connected between the buoyant cable of the antenna element and a second buoyant cable. The second buoyant cable extends inward toward a submarine.
The broadband in-line amplifier is designed to operate on the frequencies of interest. These frequencies are those between 10 kHz-200 kHz and 2 MHz-160 Mz. The frequencies referred to in the specification are as follows: VLF (very low frequency) 3-30 kHz, LF (low frequency) 30-300 kHz, MF (medium frequency) 300 kHz-3 MHz, HF (high frequency) 3-30 MHz and VHF (very high frequency) 30-300 MHz.
(2) Description of the Prior Art
Previous amplifiers could neither amplify nor pass VLF/LF signals. These VLF/LF signals were received on the portion of the shield of the coaxial feedline floating on the surface of the water, using the amplifier housing as grounding electrode and the hull of the submarine as a ground return to the seawater. The performance of such a VLF/LF antenna varied with both the amount of the antenna stored on the ship and the amount on the ocean surface. The only alternative was to build an antenna without an amplifier. This was fine for VLF/LF reception but limited to only about 12 MHz maximum by the loss in the feedline.